CNS__M4_MD5 Crypto graphyCNS__M4_MD5 Crypto graphyCNS__M4_MD5 Crypto graphy

1. BCSE309L – Cryptography and Network
Security
https://www.comparitech.com/blog/information-security/md5-algorithm-with-examples/

2. Message Digest (MD5)
2

3. Message Digest (MD5)
• MD5 was developed in 1991 by Ronald Rivest
• MD5 is a cryptographic hash function algorithm that
takes the message as input of any length and changes
it into a fixed-length message of 16 bytes.
• MD5 algorithm stands for the message-digest
algorithm.
• The output of MD5 (Digest size) is always 128 bits.
3
Plaintext = multiples of 512 bits
Message digest = 128 bits

4. Message Digest (MD5)
• Uses
 It is used for file authentication.
 In a web application, it is used for security
purposes. e.g. Secure password of users etc.
 Using this algorithm, We can store our password in
128 bits format
4

5. Message Digest (MD5)
• Working of MD5 Algorithm
1. Append Padding Bits
2. Append Length Bits
3. Initialize MD buffer
4. Process Each 512-bit Block
5

6. Message Digest (MD5)
6
L  No. of blocks

7. Message Digest (MD5)
1. Append Padding Bits
 In the first step, we add padding bits in the original
message in such a way that the total length of the
message is 64 bits less than the exact multiple of 512
7
Length(original message + padding bits) = 512 * i – 64 where i = 1,2,3 . . .

8. Message Digest (MD5)
Example:
• Plaintext Message: “ They are deterministic”
T  54  01010100
h  68  01101000
e  65  01100101
y  79  01111001
…
01010100 01101000 01100101 01111001 00100000 01100001
01110010 01100101 00100000 01100100 01100101 01110100
01100101 01110010 01101101 01101001 01101110 01101001
01110011 01110100 01101001 01100011
Total 22 letters including blank space  22*8 = 176 bits
ASCII

9. 9

10. Message Digest (MD5)
10
Length(original message + padding bits) = 512 * i – 64 where i = 1,2,3 . . .
= 512*1-64
= 512 – 64
= 448
Original message + padding = 448
176 + padding bits = 448
padding bits = 448-176
= 272 bits
= 1(1 bit) + 0 (271 bits)
01010100 01101000 01100101 01111001 00100000 01100001 01110010 01100101
00100000 01100100 01100101 01110100 01100101 01110010 01101101 01101001
01101110 01101001 01110011 01110100 01101001 01100011 10000000 00000000
00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
272/8=34
Append Padding Bits

11. Message Digest (MD5)
2. Append Length Bits
 Add length bit in the output of the first step in such a way
that the total number of the bits is the perfect multiple of
512.
 Simply, here we add the 64-bit as a length bit in the output of
the first step.
i.e. output of first step = 512 * n – 64
length bits = 64.
 After adding both, the length of the message = 512 * n 11

12. Message Digest (MD5)
12
01010100 01101000 01100101 01111001 00100000 01100001 01110010 01100101
00100000 01100100 01100101 01110100 01100101 01110010 01101101 01101001
01101110 01101001 01110011 01110100 01101001 01100011 10000000 00000000
00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
Append Length Bits
Length of original message = 176
= 10110000
This is the end of the padding scheme, while the preceding 56 bits are all filled up with zeros.
01010100 01101000 01100101 01111001 00100000 01100001 01110010 01100101
00100000 01100100 01100101 01110100 01100101 01110010 01101101 01101001
01101110 01101001 01110011 01110100 01101001 01100011 10000000 00000000
00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
00000000 00000000 00000000 00000000 00000000 00000000 00000000 10110000

13. Message Digest (MD5)
3. Initialize MD buffer (– to store output)
 Initialize four different buffers, namely A, B, C, and
D.
 These buffers are 32 bits each and are initialized as
follows:
13
A = 01 23 45 67
B = 89 ab cd ef
C = fe dc ba 98
D = 76 54 32 10
Each buffers= 32bits
Need 4 buffers (A, B, C, D) –
Store 32*4=128 bits

14. Message Digest (MD5)
4. Process each block:
 Each 512-bit block gets broken down further into 16 sub-
blocks of 32 bits each.
 There are four rounds of operations, with each round
utilizing all the sub-blocks, the buffers, and a constant array
value
 This constant array can be denoted as K[1]  K[64].
 Each of the sub-blocks are denoted as M[0]  M[15]
14
Length of message = 512 * n
Each block= 512 bits

15. Message Digest (MD5)
512-bit M needs to be split into sixteen 32-bit “words”
M0 – 01010100 01101000 01100101 01111001
M1 – 00100000 01100001 01110010 01100101
M2 – 00100000 01100100 01100101 01110100
M3 – 01100101 01110010 01101101 01101001
M4 – 01101110 01101001 01110011 01110100
M5 – 01101001 01100011 10000000 00000000
M6 – 00000000 00000000 00000000 00000000
M7 – 00000000 00000000 00000000 00000000
M8 – 00000000 00000000 00000000 00000000
M9 – 00000000 00000000 00000000 00000000
M10 – 00000000 00000000 00000000 00000000
M11 – 00000000 00000000 00000000 00000000
M12 – 00000000 00000000 00000000 00000000
M13 – 00000000 00000000 00000000 00000000
M14 – 00000000 00000000 00000000 00000000
M15 – 00000000 00000000 00000000 10110000

16. Message Digest (MD5)
M0 – 01010100 01101000 01100101 01111001
M1 – 00100000 01100001 01110010 01100101
M2 – 00100000 01100100 01100101 01110100
M3 – 01100101 01110010 01101101 01101001
M4 – 01101110 01101001 01110011 01110100
M5 – 01101001 01100011 10000000 00000000
M6 – 00000000 00000000 00000000 00000000
M7 – 00000000 00000000 00000000 00000000
M8 – 00000000 00000000 00000000 00000000
M9 – 00000000 00000000 00000000 00000000
M10 – 00000000 00000000 00000000 00000000
M11 – 00000000 00000000 00000000 00000000
M12 – 00000000 00000000 00000000 00000000
M13 – 00000000 00000000 00000000 00000000
M14 – 00000000 00000000 00000000 00000000
M15 – 00000000 00000000 00000000 10110000
M0 – 54686579
M1 – 20617265
M2 – 20646574
M3 – 65726D69
M4 – 6E697374
M5 – 69638000
M6 – 00000000
M7 – 00000000
M8 – 00000000
M9 – 00000000
M10 – 00000000
M11 – 00000000
M12 – 00000000
M13 – 00000000
M14 – 00000000
M15 – 000000B0

17. Message Digest (MD5)
• Each of these M inputs (512 bits)
are used in every single round,
they are added in different orders.
In second round:
M1, M6, M11, M0, M5, M10, M15, M4,
M9, M14, M3, M8, M13, M2, M7, M12
In third round
M5, M8, M11, M14, M1, M4, M7, M10,
M13, M0, M3, M6, M9, M12, M15, M2
In fourth round
M0, M7, M14, M5, M12, M3, M10, M1,
M8, M15, M6, M13, M4, M11, M2, M9
17
Operation carried out
on Every 512 bit block

18. Message Digest (MD5)
• Initialization vector
18
A – 01234567
B – 89abcdef
C – fedcba98
D – 76543210
M0 – 54686579
M1 – 20617265
M2 – 20646574
M3 – 65726D69
M4 – 6E697374
M5 – 69638000
M6 – 00000000
M7 – 00000000
M8 – 00000000
M9 – 00000000
M10 – 00000000
M11 – 00000000
M12 – 00000000
M13 – 00000000
M14 – 00000000
M15 – 000000B0

19. Message Digest (MD5)
• Initialization vector
19
A – 01234567
B – 89abcdef
C – fedcba98
D – 76543210
M0 – 54686579
M1 – 20617265
M2 – 20646574
M3 – 65726D69
M4 – 6E697374
M5 – 69638000
M6 – 00000000
M7 – 00000000
M8 – 00000000
M9 – 00000000
M10 – 00000000
M11 – 00000000
M12 – 00000000
M13 – 00000000
M14 – 00000000
M15 – 000000B0

20. 20
The values for K are is derived from the formula
K1 – D76AA478
K2 – E8C7B756
K3 – 242070DB
K4 – C1BDCEEE
K5 – F57COFA
K6 – 4787C62A
K7 – A8304613
K8 – FD469501
K9 – 698098D8
K10 – 8B44F7AF
K11 – FFFF5BB1
K12 – 895CD7BE
K13 – 6B901122
K14 – FD987193
K15 – A679438E
K16 – 49B40821
K17 – F61E2562
K18 – C040B340
K19 – 265E5A51
K20 – E9B6C7AA
K21 – D62F105D
K22 – 02441453
K23 – D8A1E681
K24 – E7D3FBC8
K25 – 21E1CDE6
K26 – C33707D6
K27 – F4D50D87
K28 – 455A14ED
K29 – A9E3E905
K30 – FCEFA3F8
K31 – 676F02D9
K32 – 8D2A4C8A
K33 – FFFA3942
K34 – 8771F681
K35 – 699D6122
K36 – FDE5380C
K37– A4BEEA44
K38 – 4BDECFA9
K39 – F6BB4B60
K40 – BEBFBC70
K41 – 289B7EC6
K42 – EAA127FA
K43 – D4EF3085
K44 – 04881D05
K45 – D9D4D039
K46 – E6DB99E5
K47 – 1FA27CF8
K48 – C4AC5665
K49 – F4292244
K50 – 432AFF97
K51 – AB9423A7
K52 – FC93A039
K53 – 655B59C3
K54 – 8F0CCC92
K55 – FFEFF47D
K56 – 85845DD1
K57 – 6FA87E4F
K58 – FE2CE6E0
K59 – A3014314
K60 – 4E0811A1
K61 – F7537E82
K62 – BD3AF235
K63 – 2AD7D2BB
K64 – EB86D391
Round1 Round2 Round3 Round4
Round Operation

21. Message Digest (MD5)
Each block  4 rounds of operation
• In each round  16 operations are performed
– Total  64 operations are performed in 4 rounds.
• 1st round  16 operations will be performed
• 2nd round  16 operations will be performed
• 3rd round  16 operations will be performed
• 4th round  16 operations will be performed.
• We apply a different function on each round i.e. for the
– 1st round we apply the F function,
– 2nd G function
– 3rd for the H function
– 4th for the I function.
21

22. Message Digest (MD5)
• Each round has 16 steps of the form:
b = b+((a+f(b,c,d)+M[i]+K[i])<<<s)
22
• Constant array : K[1]  K[64].
• K[1-16]
• K[17-32]
• K[33-48]
• K[49-64]
• Each of the sub-blocks : M[0]  M[15]
• M[0]  32bits
• M[1]  32bits
• …
• M[15]  32bits
g(b,c,d) is a different nonlinear
function in each round (F,G,H,I)

23. Message Digest (MD5)
• g(b,c,d) is a different nonlinear function in each round
(F,G,H,I)
• Perform OR, AND, XOR, and NOT (basically these are
logic gates) for calculating functions
• Use 3 buffers for each function
23
F(B,C,D) = (B AND C) OR (NOT B AND D)
G(B,C,D) = (B AND C) OR (C AND NOT D)
H(B,C,D) = B XOR C XOR D
I(B,C,D) = C XOR (B OR NOT D)

24. The values for K are is derived from the formula
K1 – D76AA478
K2 – E8C7B756
K3 – 242070DB
K4 – C1BDCEEE
K5 – F57COFA
K6 – 4787C62A
K7 – A8304613
K8 – FD469501
K9 – 698098D8
K10 – 8B44F7AF
K11 – FFFF5BB1
K12 – 895CD7BE
K13 – 6B901122
K14 – FD987193
K15 – A679438E
K16 – 49B40821
K17 – F61E2562
K18 – C040B340
K19 – 265E5A51
K20 – E9B6C7AA
K21 – D62F105D
K22 – 02441453
K23 – D8A1E681
K24 – E7D3FBC8
K25 – 21E1CDE6
K26 – C33707D6
K27 – F4D50D87
K28 – 455A14ED
K29 – A9E3E905
K30 – FCEFA3F8
K31 – 676F02D9
K32 – 8D2A4C8A
K33 – FFFA3942
K34 – 8771F681
K35 – 699D6122
K36 – FDE5380C
K37– A4BEEA44
K38 – 4BDECFA9
K39 – F6BB4B60
K40 – BEBFBC70
K41 – 289B7EC6
K42 – EAA127FA
K43 – D4EF3085
K44 – 04881D05
K45 – D9D4D039
K46 – E6DB99E5
K47 – 1FA27CF8
K48 – C4AC5665
K49 – F4292244
K50 – 432AFF97
K51 – AB9423A7
K52 – FC93A039
K53 – 655B59C3
K54 – 8F0CCC92
K55 – FFEFF47D
K56 – 85845DD1
K57 – 6FA87E4F
K58 – FE2CE6E0
K59 – A3014314
K60 – 4E0811A1
K61 – F7537E82
K62 – BD3AF235
K63 – 2AD7D2BB
K64 – EB86D391
MD5 F, G, H and I functions
F(B, C, D) = (B∧C)∨(¬B∧D)
G(B, C, D) = (B∧D)∨(C∧¬D)
H(B, C, D) =B⊕C⊕D
I(B, C, D) = C⊕(B∨¬D)
Round1 Round2 Round3 Round4
A – 01234567
B – 89abcdef
C – fedcba98
D – 76543210
M0 – 54686579
M1 – 20617265
M2 – 20646574
M3 – 65726D69
M4 – 6E697374
M5 – 69638000
M6 – 00000000
M7 – 00000000
M8 – 00000000
M9 – 00000000
M10 – 00000000
M11 – 00000000
M12 – 00000000
M13 – 00000000
M14 – 00000000
M15 – 000000B0

25. 25
MD5 F, G, H and I functions
F(B, C, D) = (B∧C)∨(¬B∧D)
G(B, C, D) = (B∧D)∨(C∧¬D)
H(B, C, D) =B⊕C⊕D
I(B, C, D) = C⊕(B∨¬D)
F (89abcdef, fedcba98, 76543210) = (89abcdef AND fedcba98) OR (NOT-89abcdef AND 76543210)
F(B, C, D) = 88888888 OR 76543210
= fedcba98
Modular Addition  (X + Y) mod Z
X01234567
Yfedcba98
Z100000000 (232)
(X + Y) mod Z
= (01234567 + fedcba98) mod 100000000
= ffffffff mod 100000000
= ffffffff

26. 26
MD5 F, G, H and I functions
F(B, C, D) = (B∧C)∨(¬B∧D)
G(B, C, D) = (B∧D)∨(C∧¬D)
H(B, C, D) =B⊕C⊕D
I(B, C, D) = C⊕(B∨¬D)
F (89abcdef, fedcba98, 76543210) = (89abcdef AND fedcba98) OR (NOT-89abcdef AND 76543210)
F(B, C, D) = 88888888 OR 76543210
= fedcba98
Modular Addition  ffffffff
(X + Y) mod Z
X  M0 = 54686579
Y ffffffff
Z100000000 (232)
(X + Y) mod Z
= (54686579 + ffffffff) mod 100000000
= 154686578

27. 27
MD5 F, G, H and I functions
F(B, C, D) = (B∧C)∨(¬B∧D)
G(B, C, D) = (B∧D)∨(C∧¬D)
H(B, C, D) =B⊕C⊕D
I(B, C, D) = C⊕(B∨¬D)
F (89abcdef, fedcba98, 76543210) = (89abcdef AND fedcba98) OR (NOT-89abcdef AND 76543210)
F(B, C, D) = 88888888 OR 76543210
= fedcba98
Modular Addition  154686578
(X + Y) mod Z
X  K0 = d76aa478
Y 154686578
Z100000000 (232)
(X + Y) mod Z
= (d76aa478 + 54686578) mod 100000000
= 2bd309f0

28. 28
The values for K are is derived from the formula
K1 – D76AA478
K2 – E8C7B756
K3 – 242070DB
K4 – C1BDCEEE
K5 – F57COFA
K6 – 4787C62A
K7 – A8304613
K8 – FD469501
K9 – 698098D8
K10 – 8B44F7AF
K11 – FFFF5BB1
K12 – 895CD7BE
K13 – 6B901122
K14 – FD987193
K15 – A679438E
K16 – 49B40821
K17 – F61E2562
K18 – C040B340
K19 – 265E5A51
K20 – E9B6C7AA
K21 – D62F105D
K22 – 02441453
K23 – D8A1E681
K24 – E7D3FBC8
K25 – 21E1CDE6
K26 – C33707D6
K27 – F4D50D87
K28 – 455A14ED
K29 – A9E3E905
K30 – FCEFA3F8
K31 – 676F02D9
K32 – 8D2A4C8A
K33 – FFFA3942
K34 – 8771F681
K35 – 699D6122
K36 – FDE5380C
K37– A4BEEA44
K38 – 4BDECFA9
K39 – F6BB4B60
K40 – BEBFBC70
K41 – 289B7EC6
K42 – EAA127FA
K43 – D4EF3085
K44 – 04881D05
K45 – D9D4D039
K46 – E6DB99E5
K47 – 1FA27CF8
K48 – C4AC5665
K49 – F4292244
K50 – 432AFF97
K51 – AB9423A7
K52 – FC93A039
K53 – 655B59C3
K54 – 8F0CCC92
K55 – FFEFF47D
K56 – 85845DD1
K57 – 6FA87E4F
K58 – FE2CE6E0
K59 – A3014314
K60 – 4E0811A1
K61 – F7537E82
K62 – BD3AF235
K63 – 2AD7D2BB
K64 – EB86D391
MD5 F, G, H and I functions
F(B, C, D) = (B∧C)∨(¬B∧D)
G(B, C, D) = (B∧D)∨(C∧¬D)
H(B, C, D) =B⊕C⊕D
I(B, C, D) = C⊕(B∨¬D)
Round1 Round2 Round3 Round4

29. 29
MD5 F, G, H and I functions
F(B, C, D) = (B∧C)∨(¬B∧D)
G(B, C, D) = (B∧D)∨(C∧¬D)
H(B, C, D) =B⊕C⊕D
I(B, C, D) = C⊕(B∨¬D)
F (89abcdef, fedcba98, 76543210) = (89abcdef AND fedcba98) OR (NOT-89abcdef AND 76543210)
F(B, C, D) = 88888888 OR 76543210
= fedcba98
Modular Addition  2bd309f0
Left bit shift
0010 1011 1101 0011 0000 1001 1111 0000

30. 001 0101 1110 1001 1000 0100 1111 1000 0xxx xxxx
Shift 7 bits left
1110 1001 1000 0100 1111 1000 0001 0101
In hexa
e984f815
A – 01234567
B – 89abcdef
C – fedcba98
D – 76543210
(X + Y) mod Z
X  B = 89abcdef
Y e984f815
Z100000000 (232)
(X + Y) mod Z
= (89abcdef + e984f895) mod 100000000
= 7330C604
A – 76543210
B – 7330c604
C – 89abcdef
D – fedcba98
2bd309f0
First operation in Round1 is completed
Similarly do other 63 operations and generate
the final Message Digest of 128 bits